I see the ultimate problem (outside of cost) with the express train is that the main station (Union) is really not all that central (sure, east-west central, but not north-south). Unless you are working "on Bay Street" or live in one of the new condos close to it, you are going to have to get there either on taxi or public transport. If you take a taxi you might as well take it all the way to the airport as the cost and time will be comparable while public transport will add a lot of extra time even if you are on a subway line--not to mention the hassle of luggage. If I live at, say, Yonge and St. Claire would I really want to give myself an extra hour to walk to the subway, take it to union and then wait for my train? Sure the ride to YYZ from union is 25 minutes, but very few people will not have a lengthy commute to get to Union. The other two stations are really only handy if you live quite close to them.